mkdir

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

No annotations are provided, so the description carries the full burden of behavioral disclosure. It only states the basic action of creating a directory and mentions the write tool's behavior, but does not disclose error conditions (e.g., what happens if the directory exists when parents is false), permission requirements, or return behavior. This is a significant gap for a tool with no annotation support.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is extremely concise—two sentences, with the primary purpose front-loaded and the important usage note following. Every sentence earns its place, with no waste. It is appropriately sized for a simple tool.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a simple tool, the description is fairly complete. It covers the core action and includes a valuable note about the write tool's behavior to avoid redundancy. However, it omits details about error handling (e.g., behavior when the directory already exists) and does not describe return values, though the schema partially covers error behavior via the 'parents' flag. Overall, it is adequate for typical usage.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The input schema has 100% description coverage for both parameters, including default behavior for 'parents'. The description adds no additional parameter semantics beyond what the schema already provides. The baseline of 3 applies because the schema fully documents the parameters.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description states a clear verb and resource: 'Creates a new directory.' It is specific and unambiguous, distinguishing itself from siblings like write, read, and remove by its directory-focused action. However, it does not explicitly contrast itself with sibling tools beyond the write tool note, so it lacks full differentiation.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description explicitly tells agents when NOT to use mkdir: 'You DO NOT need to call mkdir prior to writing a new file with the write tool.' This is a strong usage exclusion that prevents unnecessary calls. It does not explicitly state when to use it, but the purpose is clear enough that usage is implied.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.